TECHNICAL UNIVERSITY OF CLUJ-NAPOCA
ACTA TECHNICA NAPOCENSIS
Series: Applied Mathematics, Mechanics, and Engineering Vol. 62, Issue III, September, 2019
EXOSKELETON ROBOTIC SYSTEMS USED AS A TOOL FOR CARDIAC
REHABILITATION
Bogdan MOCAN, Mircea FULEA, Anca Daniela FĂRCAȘ, Mihaela MOCAN
Abstract: Rehabilitation domain is one of the most dynamic field for exoskeletons robots, which are de-signed to assist patients in developing prescribed therapies. The exoskeletons should be able to respond to any command made by the patient or by the rehabilitation specialist. Thanks to technological advancements in mechatronics field, such robotic systems, greatly improve both the sensing and manipulation strengths of a patient. Within this paper the focus will be on identifying and performance evaluation of the existing medical exoskeletons used in cardiac rehabilitation therapy. To highlight the performance of exoskeletons in cardiac rehabilitation therapy, they were classified into several different categories based on their’ per-formance features. Further, a non-systematic literature review was performed using ScienceDirect biblio-metric database to retrieve publications related to “exoskeleton robots” used in different medical thera-pies. A gap in scientific studies published in peer-reviewed literature on the commercial exoskeletons con-cerning cardiac rehabilitation was identified. Technology is rapidly evolving, and concerted investment into larger scale clinical trials is needed to identify the real benefits of the robotic skeletons in cardiac rehabilitation. Also, data from randomized clinical trials will be necessary to convince investors of the importance and benefits of funding robotic exoskeletons for patients with cardiac problems to support re-habilitation therapies.
Key words: robotics, exoskeletons, rehabilitation, cardiac rehabilitation exoskeletons.
1. INTRODUCTION
Every year, 15 million people worldwide suffer a stroke (1). More than 85% of them survive, but only 10% are fully recovered (2). Moreover, in-dividuals with a form of paraplegia present 70% greater risk of developing cardiovascular dis-eases as compared with gender and age matched able-bodied individuals (2). In fact, cardiovas-cular disease is now considered the leading cause of mortality in elderly living in modern world (3). An effective rehabilitation therapy, especially motor therapy, should address patient needs, and should have the necessary intensity and duration to retrain the muscles and reactivate the affected nervous systems zones (4).
Motor rehabilitation is often performed in pa-tients who have suffered damage to their nerv-ous system such as stroke patients, and seldom in patients with cardiac disease who show long-lasting abnormalities in sweating and heart rate variability (5).
Most of these motor rehabilitation treatments need sessions of physical therapy to improve joint range of motion, strengthen muscles, re-store cardiac functional capabilities, and resolve impairments (4).
However, the number of qualified human thera-pists who can provide this treatment is limited, while the demand is growing, particularly as ag-ing populations (6). While there remain a few procedures that only human therapists can do, many rehabilitation exercises are highly repeti-tive (7). This is where robotic systems outper-form the humans. They can peroutper-form the same task(s) with precision and without exhaustion or loss of attention and concentration (8).
robotic systems greatly improve both the sensing and manipulation strengths of a human (9). Within this paper the focus will be on perfor-mance evaluation of the existing medical exo-skeletons and highlighting those used in cardiac rehabilitation therapy.
2. SURVEY OF REHABILITATION
EXOSKELETONS ROBOTS
Repetitive task-oriented movements are the single most important variable of cardiac rehabilitation and have a therapeutic gain; the literature suggests that an elderly patient recovering from heart failure (HF) must play an active role in the rehabilitation process if improvement occurs (10), (11). Many exoskeletons are aimed at rehabilitation delivery. However, a limited number have demonstrated clinical efficacy, and few are currently used for pa-tient care in clinical environments.
Thus, to highlight the need for rehabilitation us-ing exoskeleton robotic systems, we should sur-vey the goals of existing cardiac rehabilitation therapies (4), (8):
Increase activity: in a conventional approach it is done using different rehabilitation equipment like Thera-bands, pegboards, or blocks.
Provide intense, repetitive and engaging exer-cises: conventionally, the therapist’s devotion and enthusiasm play an important role in provid-ing different exercises/ therapies.
Provide assistance: traditionally is accom-plished with the help of therapists, splints, and arm-supports.
Improve assessment: conventionally is achieved by force gauges, goniometers, and timers. Provide feedback: for the patients the feedback is very important and motivating. The feedback should be visual, auditory, or tactile.
In order to highlight the performance of existing exoskeletons in different rehabilitation therapy, a short classification should be of made. Thus, exoskeletons can be divided into several differ-ent categories based on their’ specific features (eq. technical characteristics, the fact of being active or passive, how they are controlled, etc.) (12), (13), (14) or about how it helps the patient: Patient’s body parts that are “motorised” by
the exoskeleton:
o full body exoskeleton;
o upper extremities: arms and torso;
o lower extremities: legs, hip, knee, or ankle
only, knee, ankle, knee-ankle or hip-knee-ankle.
Active or passive exoskeletons:
o active or powered exoskeletons - use
batter-ies or power sources to run actuators and to control sensors
• static exoskeletons - the actuators always need to be turned on for the exoskeleton to maintain its shape;
• dynamic exoskeletons – the actuators are always turned on and the device can be many times more energy efficient.
o passive exoskeletons: do not have any
electrical power source and can be used for: • weight re-distribution: springs and lock-ing mechanisms divert the weight of the patient into the ground supporting them; • energy capture: ankle spring-clutch
exo-skeletons have been shown to improve walking efficiency, while spring-dynamo knee exoskeletons can be used to charge a battery;
• dampening: some passive exoskeletons have been designed as shock absorbers; • locking: passive exoskeletons are
de-signed to be unobtrusive until they are locked into a pose, allowing the user to sit or to squat in a certain position.
o pseudo-passive exoskeletons: this kind of
exoskeletons have batteries, sensors, and other electronics, but they are not used to provide actuation.
o hybrid - exoskeletons are wearables that
have all the necessary controllers and sen-sors of a powered exoskeleton but uses FES (functional electrical stimulation) of the hu-man muscles as actuators.
Fixed or mobile exoskeleton:
o fixed exoskeleton: the device is tethered,
at-tached to a wall, a bracket or suspended from the air by a fixed hook and harness;
o supported: the exoskeleton is attached to an
overhead rail, is supported by a moving frame or in some cases, supported by an ad-jacent wheeled robot. These configurations allow for the heavy motors, controllers and batteries to be externally supported while still granting mobility to exoskeleton wearer.
o mobile: the user and exoskeleton can move
Type of control (user-machine-interface):
o joystick: reserved for exoskeletons that
pro-vide 100% of the energy for motion needed by the wearer;
o buttons or control panels: the exoskeleton is
placed in different pre-programmed modes. The control panel does not have to be within the exoskeleton, some previous models have them on a wrist trap, integrated into walking supports such as crutches or held by a super-visor next to the user;
o mind-controlled: using an electrode/
senso-rial skull cap;
o sensors based control: current exoskeletons
models can have forty and more different in-tegrated sensors that monitor joints torque, joints rotations, tilt, or pressure and they can collect users’ arms and legs nerve signals;
o without electric control: passive
exoskele-tons devices have no control equipment and no actuation system.
Type of built materials (15):
o rigid materials as metals or carbon fibre; o flexible materials used into the entire
con-struction (soft exoskeleton).
Based on the above classification there are plenty of applications where exoskeletons robotic sys-tems could be implemented: medical, military, ci-vilian areas, industry, etc. Thus, we can divide the development of exoskeleton robotic systems into two directions in terms of posible applications: medical and nonmedical (16).
Concerning medical applications, the rehabilita-tion exoskeletons can be configured such that they provide the necessary amount of assistance, aiding a patient's efforts to a limited extent and thus providing a rigorous, targeted therapy session (17). A non-systematic literature review was per-formed, within this paper, using ScienceDirect bibliometric database to retrieve publications re-lated to “exoskeleton robotic systems” used in different medical applications. In the keywords field of the ScienceDirect bibliometric search engine, the following keywords were used: “ex-oskeleton robotic systems; therapeutic rehabili-tation exoskeletons; and cardiac rehabilirehabili-tation exoskeletons” (Figure 1).
Figure 1. Publications related to the keywords: ton robotic systems; therapeutic rehabilitation exoskele-tons; cardiac rehabilitation exoskeletons.
The rate at which robotic exoskeleton technol-ogy is advancing makes it difficult to summarize the current state of the art in this field; new exo-skeletons robotic models and manufacturing companies are appearing continuously (18). What we can say with certainty is that there is a lack of scientific studies published in peer-re-viewed literature about the commercial robotic exoskeletons (Figure 1) used in therapeutic bilitation strategies in general and cardiac reha-bilitation therapies in special.
Companies are trying to make profit from their products and do not necessarily want to adver-tise any drawbacks of their equipment, provid-ing little incentive for them to publish studies evaluating their robotic exoskeletons in scien-tific journals. The intrinsic capabilities of robot-ics systems in producing highly repetitive, and precisely controllable motions makes them de-sirable for rehabilitation purposes (19). Proce-dures for rehabilitation therapy can be based ei-ther on passive or active movements (9) devel-oped by exoskeletons systems. Passive devices offer limited rehabilitation features and no sen-sory feedback data is available to therapists. That’s why in the next paragraphs we will ana-lyze some exoskeleton robotic systems that are capable to generate active movements and to support a rehabilitation therapy.
girdle, glenohumeral joint, elbow and wrist. It has six active, and two passive DOFs. CLEVER-arm is enhanced with games software technol-ogy to increase the engagement of patients in therapy approach. Integration of gaming with ro-botics-based rehabilitation therapy has proven to be successful for therapeutic goals (20). CLEVERarm uses Augmented Reality (AR) technology developed by Hololens to provide a different gaming experience to patients.
The EksoTM GT over ground robotic exoskeleton
which weighs about 28 kg, provides maximal external support and generates flexion and ex-tension movements at the hips and knees using motors in a manner that replicates and allows for walking. This is the first exoskeleton to be ap-proved by the FDA for those recovering from a stroke. The EksoTM is actuated powered
hip-knee exoskeleton with variable assist controls, and it can apply power from 0 ÷ 100% as needed. Some very new researches have highlighted the effectiveness of the EksoTM exoskeleton in
car-diac rehabilitation therapy (2).
The REX exoskeleton robot provides a stable platform for users to perform exercises in all po-sitions, like an upright position, or walking back-wards, sideways, in a lunge or squat position (21). Unlike any other exoskeleton available, REX does not require the use of poles or sticks to bal-ance whilst users are walking or performing exer-cises. This allows users arms to be free to use any regular equipment found in a gym.
Wrist Gimbal is a 3 DOFs exoskeleton robot de-veloped for forearm and wrist rehabilitation and it has pinched the attention of the researchers due to its unique wrist design which corrects the wrist joint axis misalignment between user and the robot. Wrist Gimbal can generate forearm pronation/ supination, wrist flexion/ extension and wrist ulna/radial deviation.
Perry and Rosen have designed anthropometric 7 DOFs active exoskeleton system, known as EXO-7. The anthropomorphic nature of the joints combined with negligible backlash in seven force-reflecting articulations is set as the original characteristic of the EXO-7. Prior to the development of EXO-7, the research team de-veloped few prototypes with lesser DOF and the latest prototype, EXO-7 was designed consider-ing human anthropometry (22).
This 7 DOFs exoskeleton was developed
primarily to assist the elderly and disabled peo-ple. The exoskeleton was mounted on a wheel-chair and the link configuration uses both paral-lel and serial kinematic structure.
There are more commercial or prototypes exo-skeletons robots which have demonstrated more or less technical and economic feasibility; in the near future we expect that more progress will be made in design and in motion control and “force and moment” transfer to the patient’s body of re-habilitation robots for providing biologically plausible autonomous therapy.
3. BENEFITS OF ROBOTIC EXOSKELETONS
Different models of powered exoskeletons are now commercially available for rehabilitation. However, there is still a limited accessibility to exoskeletons in clinical settings, partly because of their prohibitive cost and due to the high level of training required before supervising individu-als in different health-related outcomes. From the clinical health-prospective, several reports (7) have demonstrated that exoskeleton training is safe and likely to be used in different settings to encourage over ground ambulation (23), (24). These studies provided preliminary evidence on the efficacy of exoskeletons on cardiovascular health, energy expenditure, body composition, gait parameters, level of physical activity and quality of life.
4. CONCLUSIONS AND FUTURE TRENDS
New technological achievements in robotic exo-skeletons have enabled this equipment to reach the commercial market but the physical connec-tions between humans - device, and control of exoskeletons are still major problems to their success on the market. Many robotic exoskeletal systems are bulky, very complex to operate, costly and heavy which limit wide-spread use of them in everyday life for rehabilitation.
exoskeleton tries to transfer mechanical power to the human body, it can result in tissue com-pression or breakage rather than power transmis-sion. In addition, the robot exoskeleton can in-duce localized pressure on both soft and hard hu-man tissues, resulting in pain for the patient that limits the exoskeleton effectiveness.
Considering the new trends in technology devel-opment, a greater push for documenting and identification the human performance with ro-botic exoskeletons and performing clinical trials and studies on patient populations and in cardiac therapy rehabilitation is needed. There is a lack of data on the cardiac patients using these exo-skeletons, both for patient’s performance aug-mentation and for clinical scopes (eq. cardiac therapeutic rehabilitation). Several research groups and companies are publishing biome-chanical and physiological measurements on us-ers/ patients wearing robotic exoskeletons in dif-ferent scenarios. There is a race to develop exo-skeleton proprietary technologies rather than to move the scientific knowledge forward. Simi-larly, different reviews of the literature indicate that there are only a few scientific evidences that robotic exoskeletons have long-term beneficial effects on the mobility or quality of life in lematic patients and more about cardiac prob-lems patients. Technology is rapidly evolving and concerted investment into larger scale cal trials is needed. Data from randomized clini-cal trials will be necessary to convince investors of the importance and benefits of funding the de-velopment of robotic exoskeleton systems for patients with cardiac problems to support reha-bilitation therapies.
7. ACKNOWLEDGMENTS
The staff of Laboratory for Robotics from the Technical University of Cluj-Napoca are grate-fully thanked for making this research possible.
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Sisteme Robotice de Tip Exoschelet Folosite ca Mijloc de Reabilitare Cardiacă
Rezumat:. Reabilitarea este una dintre cele mai dinamice domenii pentru roboții de tip exoschelet, care sunt concepuți pentru a ajuta pacienții să urmeze terapiile prescrise. Exoscheletele trebuie să fie capabile să răspundă oricărei comenzi date de pacient sau de specialistul în reabilitare. Datorită dezvoltărilor tehnologice în mecatronică, astfel de sisteme robotice îmbunătățesc foarte mult capacitatea de deplasare și manipulare a unui pacient. În această lucrare, accentul va fi pus pe identificarea și evaluarea performanțelor exoscheletelor medicale existente pe piață, utilizate în terapia de reabilitare cardiacă. Pentru a evidenția performanța exoscheletelor în terapia de reabilitare cardiacă, acestea au fost clasificate în mai multe categorii pe baza caracteristicilor lor de performanță. Mai mult, utilizând baza de date bibliometrică ScienceDirect s-a realizat o analiză nesistematică a literaturii de specialitate pentru a identifica publicații despre "exoschelete" utilizate în diverse aplicații terapii medicale. A fost identificată o lipsă a studiile științifice publicate în literatura de specialitate privind folosirea exoschelete robotice în reabilitarea cardiacă. Tehnologia evoluează rapid și în acest context sunt necesare investiții concertate în studii clinice mai ample pentru investigarea și identificarea beneficiilor reale ale utilizării exoscheletelor în reabilitarea cardiacă. De asemenea, vor fi necesare date din studii clinice randomizate pentru a convinge investitorii cu privire la importanța și beneficiile finanțării dezvoltării sistemelor robotice de tip exoschelet pentru pacienții cu probleme cardiace în vederea sprijinirii terapiilor de reabilitare.
Eng. Bogdan MOCAN, PhD, Assoc.Prof., Eng., Technical University of Cluj-Napoca, Department of Design Engineering and Robotics, [email protected], B-dul Muncii no.103-105, Cluj-Napoca, Romania.
Mircea FULEA, PhD, Assoc.Prof., Eng., Technical University of Cluj-Napoca, Department of De-sign Engineering and Robotics, [email protected]
Dr. Anca Daniela FĂRCAȘ, Lecturer, Iuliu Haţieganu University of Medicine and Pharmacy,
Car-diology Department, Emergency Clinical County Hospital, Cluj-Napoca, Romania
Dr. Mihaela MOCAN, PhD. Lecturer, Iuliu Haţieganu University of Medicine and Pharmacy,
